Capacitor replacement question.

[Hextejas]

I am reading the thread about tearing down a Tektronix scope. he is replacing a 11000MFD 15v with a 22000MFD 25v.
He seems to know what he is doing though whenever I replace capacitors I try to get the same sizes and types.
So, as he did, can I always go bigger when replacing capacitors ?

[ataradov]

Not always. Depends on the capacitor location in the circuit.

You can almost always go higher on bulk capacitors in the power supply. But if capacitor is used in a filter, changing the specs will change the filter characteristics.

[Zero999]

Yes, in a bulk filtering application, it's generally fine to go larger, the main downside is the inrush current surge will increase, which could cause problems with the fuse and/or rectifiers blowing.

[Tandy]

A lot of switch mode power supplies use cheap high ESR capacitors for smoothing that heat up due to ripple. Using low ESR capacitors generally results in longer life, also uprating to a higher capacitance also means that, assuming the dielectric is the same thickness then extra capacitance is achieved by increasing the plate area. As the plate area increases, the ESR will go down reducing the damage caused by heating.

Also if you think about it increasing the capacitance means that the replacement has a head start so to speak. As it ages it will take a while before the new higher value degrades to the lower capacitance of the original, therefore the time before it needs replacing again will be extended.